What Is the Difference between Smooth and Skeletal Muscles?

There are many different types of tissue in the human body that all work together to allow people to function on a daily basis. One such type is muscular tissue. Most people realize that muscles contract to help us move or perform physical tasks, but there are actually different types of muscle. Two of these types, smooth and skeletal muscles, differ primarily in function, composition, and structure.

There are three types of muscular tissue in the body: smooth, skeletal, and striated muscle. Smooth muscle refers to much of the muscle that lines the body's tubular systems. Striated, more commonly referred to as cardiac muscle, is located in the heart and operates to contract in time units. Skeletal muscle is the most familiar type of muscle, and this is defined by that which is attached to bones, making movement possible.

Although smooth and skeletal muscles vary in many ways, they are also similar in nature. All muscle tissue contracts, usually initiated by electrical stimulation of the nervous system. There are basically four ways in which all muscle tissue overlaps. Understanding these four commonalities can improve comprehension of the basic differences.

Two of the four commonalities have already been discussed: ability to contract and excitability, which refers to the characteristic electrical stimulation. The other two overlapping muscular features are the ability to extend and return to original shape, which both play into muscle contraction. Cardiac, smooth, and skeletal muscles all possess these characteristics, hence their classification as muscles.

The differences between these types of muscle are stark in comparison to their similarities. Smooth muscle is exclusively found as the lining of many tubular structures of the body. These structures include the intestines, stomach, and blood vessels. When blood needs to be forced to a location against gravity, it relies on smooth muscle to aid its transportation. In this manner, smooth muscle allows for the movement of substances throughout the body.

Skeletal muscle is named for its location in the body in close proximity to the skeleton. When you see the biceps of a ripped individual bulge or the working quads of a marathon runner, you are witnessing skeletal muscle at work. Think of two bones with muscle between them attached through cartilaginous structures known as ligaments. When a muscle contracts, it pulls on these ligaments, causing the bones, in turn, to move. This is how skeletal muscle works to move bones.

Impulses from the nervous system tell the skeletal muscles when and how to act. These muscles can also be contracted voluntarily, whereas smooth muscle relies on the subconscious involuntary action of the nervous system. This is another primary difference between smooth and skeletal muscles. Although similar in some ways and different in many others, smooth and skeletal muscles are both important aspects of a healthily functioning human body.